Flame-resistant polycarbonate containing units from halogenated triphenolbenzamido compounds

ABSTRACT

Flame-resistant thermoplastic branched polycarbonates of high molecular weight are prepared from: 
     (1) a carbonate precursor; 
     (2) at least one dihydroxyaromatic compound of formula: ##STR1##  where: R is a single bond, or a substituted or non-substituted linear or branched C 1  -C 5  alkylene radical, or a group chosen from O, S, SO 2  and CO; 
     X and Y, which may be the same or different, are H or CH 3  ; 
     m and n, which may be the same or different, are whole numbers from 1 to 4; 
     (3) at least one halogenated triphenolbenzamido compound of formula: ##STR2##  where: Z is a group chosen from CO and SO 2  ; 
     R 1  is chlorine or bromine 
     p is 1 or 2.

This invention relates to thermoplastic branched polycarbonates of highmolecular weight possessing flame-resistant properties(self-extinguishing).

Polycarbonates are known in the art for their excellent physical andmechanical properties such as their high impact strength and theirconsiderable dimensional and thermal stability.

Because of the increasing requirement for materials which for safetyreasons possess not only excellent mechanical properties but alsoflame-resistant properties, various methods have been devised in the artfor making polycarbonates self-extinguishing. One of the most commonlyused methods is based on introducing halogens, mainly bromine andchlorine, into the polycarbonate. The halogens can be introduced intothe polymer in the form of additives by using generally polyhalogenatedorganic substances as described for example in U.S. Pat. No. 3,357,942,if desired together with other additives of synergic action such asantimony oxide (J. T. Howarth et al., Plastic World, p. 64-74, March1973).

It is also known to chemically bond the halogens to the polymer chain byusing bifunctional phenols such as tetrabromobisphenol A andtetrachlorobisphenol A as co-monomers in the preparation of thepolycarbonate (U.S. Pat. No. 3,334,154).

Halogenated substances of the known art, whether additives or monomersto incorporate in the polymer chain, must however be used in ratherlarge quantities to give the polycarbonate the requiredself-extinguishing properties. Although the presence of large halogenquantities in the polycarbonate on the one hand makes the polymer ableto resist the flame, on the other hand it leads to degradation of thepolycarbonate during its working, to thus cause deterioration in thephysical and mechanical properties of the non-halogenated polycarbonate.

Moreover, the high temperatures necessary for working the polycarbonatecan cause degradation of the halogenated compounds, with release ofhydrohalogen acids and consequent damage to the machines by corrosion.

Thus the technical problem still unsolved is to produce polycarbonatespossessing flame-resistant properties which preserve all their inherentchemical, physical and mechanical properties intact.

It has now been found possible to solve said problem by preparingthermoplastic branched polycarbonates of high molecular weightpossessing flame-resistant properties, by using a halogenatedtriphenolbenzamido compound as co-monomer in the preparation of thepolycarbonate, said compound also acting as branching agent and beingused in small quantities which are in any event less than such as wouldlead to undesirable changes in the polymer properties.

More particularly, according to the present invention, saidthermoplastic branched polycarbonates of high molecular weightpossessing flame-resistant properties are prepared from:

(1) a carbonate precursor;

(2) at least one dihydroxyaromatic compound of formula: ##STR3## where:R is a single bond, or a substituted or non-substituted linear orbranched C₁ -C₅ alkylene radical, or a group chosen from O, S, SO₂ andCO;

X and Y, which may be the same or different, are H or CH₃ ;

m and n, which may be the same or different, are whole numbers from 1 to4;

(3) at least one halogenated triphenolbenzamido compound of formula:##STR4## where: Z is a group chosen from CO and SO₂ ;

R₁ is chlorine or bromine

p is 1 or 2.

For said polycarbonates to exhibit flame-resistant properties it issufficient for the molar ratio of (3) to (2) to be between 0.05/100 and5/100, and preferably between 0.1/100 and 3/100.

The following are some examples of dihydroxyaromatic compounds (I) whichcan be used:

4,4'-dihydroxydiphenyl

2,2-bis(4-hydroxyphenyl)propane (bisphenol A)

2,2-bis(3,5-dimethyl-4-hydroxyphenyl)propane;

bis(4-hydroxyphenyl)methane.

In addition to said dihydroxyaromatic compounds, compounds with a singlebivalent aromatic ring such as resorcin and hydroquinone can also beused.

The halogenated triphenolbenzamido compounds (3) of formula II are newand can be prepared using known methods of organic chemistry. Forexample, if Z is CO, they can be prepared by reacting1,3,5-benzenetricarboxylic acid trichloride with an aromatic amine offormula: ##STR5## where: Z, R₁ and p have the aforesaid meaning.

By conducting the reaction in an organic solvent such as acetone at atemperature of about 50°-60° C. and using a molar amine/acid chlorideratio which is double the stoichiometric. The compounds in which Z is SOcan be prepared in a similar manner by using 1,3,5-benzenetrisulphonicacid trichloride in place of the benzenetricarboxylic acid trichloride.

Some examples of halogenated triphenolbenzamido compounds suitable forthe purposes of the present invention are:

1,3,5-tris(2'-hydroxy-5'-chlorophenyl)aminocarbonylbenzene;

1,3,5-tris(2'-hydroxy-5'-chlorophenyl)aminosulphonylbenzene

1,3,5-tris(4'-hydroxy-2',6'-dichlorophenyl)aminocarbonylbenzene

1,3,5-tris(4'-hydroxy-2',6'-dichlorophenyl)aminosulphonylbenzene

1,3,5-tris(2'-hydroxy-5'-bromophenyl)aminocarbonylbenzene

1,3,5-tris(4'-hydroxy-2',6'-dibromophenyl)aminosulphonylbenzene.

The carbonate precursor can be phosgene or a chloroformyl-terminatedpolycarbonate oligomer (MW between 400 and 2000) prepared by reactingphosgene with a dihydroxyaromatic compound of formula I, or it can be adiaryl, dialkyl or alkylaryl ester of carbonic acid, such as diphenylcarbonate.

The flame-resistant polycarbonates of the present invention can beprepared by reacting together, in accordance with one of thepolymerization methods usually used to produce polycarbonates, (1) acarbonate precursor, (2) a dihydroxyaromatic compound of formula I, (3)a halogenated triphenolbenzamido compound of formula II, the molar ratioof (3) to (2) varying from 0.05/100 to 5/100 and preferably from 0.1/100to 3/100.

One of the polymerization methods which can conveniently be used forpreparing said polycarbonates is interfacial polycondensation. In thismethod, the dihydroxyaromatic compound (2) and the triphenolbenzamidocompound (3) are dissolved in an aqueous sodium hydroxide solution andan organic solvent immiscible with water such as methylene chloride isthen added to this mixture.

Phosgene gas is bubbled through the obtained mixture in the presence ofa phase transfer catalyst such as triethylamine and a molecular weightregulator such as tert.butylphenol, and the reaction is maintained at atemperature of between 15° and 25° C. for a period of between 20 minutesand 6 hours.

According to a preferred embodiment of the present invention, thepolycarbonates can be prepared using as carbonate precursorschloroformyl-terminating polycarbonate oligomers, which can be preparedby interfacial reaction between phosgene and a dihydroxyaromaticcompound of formula I, in the presence of a molecular weight regulatorsuch as p-tert.butylphenol.

In practice, said chloroformyl-terminating oligomers, the molecularweight of which varies from 400 to 2000, are dissolved in awater-immiscible organic solvent and are then reacted, again by theinterfacial polycondensation method, with compounds (2) and (3) inaqueous alkaline solution, in the presence of a phase transfer catalystand a molecular weight regulator.

As an alternative to interfacial polycondensation, the polycarbonates ofthe present invention can be prepared by the known method ofpolycondensation in solution.

In this case, phosgene is bubbled through a solution of methylenechloride and pyridine containing the dihydroxyaromatic compound (2), thehalogenated triphenolbenzamido compound (3) and a monofunctional phenolas molecular weight regulator.

It is also possible to prepare said polycarbonates bytransesterification in the molten state, by reacting carbonic aciddialkyl, diaryl or alkylaryl esters as carbonate precursors with thedihydroxyaromatic compound (2) and the triphenolbenzamido compound (3)at a temperature of between 100° and 300° C. in the presence oftransesterification catalysts.

The polycarbonates prepared by any of the aforesaid methods have aprevalent molecular weight of between 20,000 and 30,000; they preserveall the inherent characteristics of thermoplastic materials intact andare suitable for processing either by injection moulding or by extrusionand/or blow-moulding. Said polycarbonates can be classified as V-0 intheir fire behaviour, evaluated by the UL94 code (underwriters'Laboratories Inc., bulletin S4) and conducted on test pieces of 3.2 mmthickness prepared by compression or injection.

According to said code the materials are classified V-0, V-1 or V-2based on the results obtained in five tests, in accordance with thefollowing criteria:

V-0: No test piece must show a combustion time exceeding 10 secondsafter removal of a bunsen flame. The total combustion time for the fivetest pieces (ten ignitions) must not exceed 50 seconds. No test piecemust allow burning particles to drip and ignite surgical cotton placedvertically under the test piece at a distance of 305 mm.

V-1: No test piece must show a combustion time exceeding 30 secondsafter removal of a bunsen flame. The total combustion time for the fivetest pieces (ten ignitions) must not exceed 250 seconds. No test piecemust allow burning particles to drip and ignite surgical cotton placedvertically under the test piece at a distance of 305 mm.

V-2: No test piece must show a combustion time exceeding 30 secondsafter removal of a bunsen flame. The total combustion time for the fivetest pieces (ten ignitions) must not exceed 250 seconds. The test piecesmay allow burning particles to drip and ignite surgical cotton placedvertically under the test piece at a distance of 305 mm.

In addition all five test pieces must pass the test prescribed by UL-94otherwise they are classified on the basis of the behaviour of the worsttest piece. For example, if one test piece shows V-2 behaviour whereasthe other four show V-0 behaviour, all five test pieces are classifiedV-2. Finally, if a test piece continues to burn for more than 30 secondsafter removing the bunsen flame, it cannot be classified under UL-94 butinstead is indicated as a flammable test piece.

The test pieces are also subjected to a fire-behaviour test inaccordance with ASTM D2863-77 which correlates the flammability of apolymer material with the oxygen concentration of the atmosphere inwhich the test piece is located. This correlation is expressed by theLOI (limiting oxygen index), i.e. the minimum oxygen percentage able tomaintain combustion of the test piece in the oxygen-nitrogen atmospherewhich flows about the test piece from the bottom upwards.

The following characteristics were also determined on the polycarbonatesof the present invention:

Intrinsic viscosity (n)

This property is determined in methylene chloride at 20° C. by anUbbelhode viscometer and is expressed in dl/g.

Melt flow index (MFI)

The melt flow index is evaluated in a melt indexer on an extrudedgranulate, under a load of 1.2 kg at a temperature of 300° C., inaccordance with ASTM D1238.

Impact strength (IZOD)

This is evaluated on notched test pieces at 0° C. in accordance withASTM D256.

Shear sensitivity (SS)

This quantity is evaluated in a melt indexer on an extruded granulate,under loads of 1.2 and 12 kg at a temperature of 300° C., in accordancewith ASTM D1238.

The following experimental examples are given for illustrative purposesonly and are not to be taken as limitative of the scope of theinvention.

EXAMPLE 1 Preparation of1,3,5-tris(2'-hydroxy-5'-chlorophenyl)aminocarbonylbenzene (in formulaII: Z is CO; R₁ is chlorine; p is 1)

32.4 g (226 mmoles) of 4-chloro-2-aminophenol dissolved in 80 ml ofacetone are placed in a 250 ml 4-neck flask fitted with a mechanicalstirrer, thermometer and reflux condenser, operating under an inert gasatmosphere.

10 g (37.6 mmols) of 1,3,5-trichlorocarbonylbenzene dissolved in 20 mlof acetone are then dripped slowly in, and the resultant mixture is keptfor 1 hour at reflux temperature (58° C.).

On termination of this period, the reaction mixture is poured into PG,124 liters of demineralized water and the product which precipitates isseparated by filtration, washed with demineralized water and dried in anoven under vacuum for 6 hours at 100° C.

In this manner 21 g of1,3,5-tris(2'-hydroxy-5'-chlorophenyl)aminocarbonylbenzene are obtainedwith a yield of 94%.

The product had the following characteristics:

Melting point (DSC): 297° C.

Equivalent weight (acidimetric): 196.3 (theoretical=195.6)

    ______________________________________                                        Elementary analysis:                                                                       C      H       N       Cl                                        ______________________________________                                        Experimental % 55.2     3.2     7.0   18.0                                    Theoretical %  55.3     3.1     7.2   18.1                                    ______________________________________                                    

The product structure was confirmed by NMR spectroscopic analysis.

EXAMPLE 2 Preparation of1,3,5-tris(4'-hydroxy-2'6'-dichlorophenyl)aminocarbonylbenzene (informula II: Z is CO; R₁ is chlorine; p is 2)

The procedure of Example 1 is followed, but using 30.1 g (169 mmoles) of2,6-dichloro-4-aminophenol instead of the 4-chloro-2-aminophenol, and7.5 g (28.2 mmoles) of 1,3,5trichlorocarbonylbenzene.

18.5 g of 1,3,5-tris(4'-hydroxy-2'6'-dichlorophenyl)aminocarbonylbenzeneare obtained with a yield of 95%.

The product had the following characteristics:

Equivalent weight (acidimetric): 229.3 (theoretical=230.1)

    ______________________________________                                        Elementary analysis:                                                                       C      H       N       Cl                                        ______________________________________                                        Experimental % 46.6     2.2     6.3   30.4                                    Theoretical %  46.9     2.2     6.1   30.8                                    ______________________________________                                    

The product structure was confirmed by NMR spectroscopic analysis.

EXAMPLE 3

84 g of bisphenol A, 2.8 g of1,3,5-tris(2'-hydroxy-5'-chlorophenyl)aminocarbonylbenzene (equal to 1.3mol % on the bisphenol A), 65.2 g of sodium hydroxide dissolved in 650ml of water, 20 mg of sodium dithionate (as reducing agent to preventthe formation of coloured by-products) and 6.3 ml of a 0.5N aqueoustriethylamine solution are fed under a nitrogen stream into a 3 literglass reactor temperature-controlled at 25° C.

2.7 g of p-tert.butylphenol dissolved in 1300 ml of methylene chlorideare then added and 44 g of phosgene gas are bubbled over a time of 30minutes through the mixture, which is subjected to vigorous stirring.

The reaction proceeds for 2 hours, aqueous sodium hydroxide (20 wt %)being added to keep the pH continuously greater than 11.

The mixture is then diluted with 500 ml of methylene chloride and theorganic phase is separated and washed successively with 300 ml of water(twice), 800 ml of 0.1N hydrochloric acid and finally with 600 mlportions of water until neutral.

The polymer is recovered by distilling the organic solvent and is driedand ground to obtain a powder.

The polycarbonate obtained in this manner is then extruded at 260° C.and the extrusion cooled and granulated.

The granules are moulded either by compression (280° C., 50 kg/cm²) orby injection (300° C.) to obtain test pieces of size 127×6.5×3.2 mm.

Five test pieces are subjected to the fire behaviour test described inUL 94. They are found to be V-0, in accordance with the data given inTable 1.

The other polycarbonate characteristics are given in Table 2.

EXAMPLE 4

Example 3 is repeated using the same operating method and reactantquantities, with the exception that no halogenated triphenolbenzamidocompound is used.

The polycarbonate obtained is found to be V-2 in accordance with UL 94(see Table 1).

The other polymer characteristics are given in Table 2.

EXAMPLE 5

253.8 g of polycarbonate chloroformyl-terminating oligomers (averagemolecular weight 681, chloroformyl terminal groups=2758 meq/kg, hydroxylterminal groups=180 meq/kg) prepared from bisphenol A and phosgene anddissolved in 900 ml of methylene chloride are fed under nitrogen into aglass reactor of 2.5 liters capacity temperature controlled at 25° C.

To the solution, mechanically stirred by a double-anchor device (300RPM) are then added, in the stated order, 50 ml of water containing 7.5g of 1,3,5-tris(2'-hydroxy-5'-chlorophenyl)aminocarbonylbenzene (equalto 1.1 mol % on the bisphenol A), 5.3 g of p-tert.butylphenol, 3.5 g ofcaustic soda, 31 mg of sodium dithionate and 7 ml of an aqueous 0.05Ntriethylamine solution. After 40 minutes 350 ml of water are addedcontaining 65.9 g of bisphenol A, 22.0 g of caustic soda and 31 mg ofsodium dithionate. 115 ml of a 20 wt % aqueous caustic soda solution arethen added over a period of 10 minutes using a metering pump.

After 3 hours the reaction mixture is poured into 2200 ml of methylenechloride; the organic phase is then separated and washed, in the statedorder, with 300 ml of water (twice), 1300 ml of 0.15N aqueous sodiumhydroxide (3 times), 900 ml of water (twice) and 1300 ml of 0.1Nhydrochloric acid, and finally with 900 ml portions of water untilneutral.

The polymer is recovered by distilling the organic solvent, and is driedand ground to obtain a powder.

The polycarbonate obtained in this manner is then extruded at 260° C.and the extrusion cooled and granulated.

The granules are moulded by injection or compression to obtain testpieces of size 127×6.5×3.2 mm.

Five test pieces are subjected to the fire behaviour test described inUL 94 and are found to be V-0, in accordance with the data given inTable 1.

The other polycarbonate characteristics are given in Table 2.

EXAMPLE 6

Example 5 is repeated using the same operating method and reactantquantities, except that 10 g of1,3,5-tris(2'-hydroxy-5'-chlorophenyl)aminocarbonylbenzene (1.4 mol % onthe bisphenol A) are added.

The polycarbonate obtained is found to be V-0 at the fire behaviourtest, evaluated in accordance with UL 94 (see Table 1).

The other polymer characteristics are given in Table 2.

EXAMPLE 7

Example 5 is repeated using the same operating method and reactantquantities, except that 5.8 g of1,3,5-tris(4'-hydroxy-2',6'-dichlorophenyl)aminocarbonylbenzene (0.7 mol% on the bisphenol A) are added.

The polycarbonate obtained is found to be V-0 at the fire behaviourtest, evaluated in accordance with UL 94 (see Table 1).

The other polymer characteristics are given in Table 2.

EXAMPLE 8

Example 5 is repeated using the same operating method and reactantquantities, except that no halogenated triphenolbenzamido compound isadded.

The polycarbonate obtained is found to be V-2 at the fire behaviourtest, evaluated in accordance with UL 94 (see Table 1).

The other polymer characteristics are given in Table 2.

                  TABLE 1                                                         ______________________________________                                             Total combustion time                                                                         Maximum combustion                                                                           Classifi-                                      of 5 test pieces (10                                                                          time per test piece                                                                          cation                                    Ex.  ignitions (seconds)                                                                           (2 ignitions) (seconds)                                                                      UL-94                                     ______________________________________                                        3    41              10             V-0                                       4    102             23             V-2                                       5    50              10             V-0                                       6    42              9              V-0                                       7    38              8              V-0                                       8    98              21             V-2                                       ______________________________________                                    

                  TABLE 2                                                         ______________________________________                                             [η] 20° C.                                                                         Impact            SS                                          CH.sub.2 Cl.sub.2                                                                      LOI    (IZOD)  MFI (300° C.;                                                                    (300° C.;                       Ex.  (dl/g)   %      (J/m)   1.2 kg)   1.2 & 12 kg)                           ______________________________________                                        3    0.545    30     720     5.9       20.1                                   4    0.515    26     718     8.0       13.5                                   5    0.562    31     790     4.7       19.5                                   6    0.558    32     703     5.0       20.0                                   7    0.607    32     762     1.0       19.8                                   8    0.533    27     723     7.2       13.4                                   ______________________________________                                    

I claim:
 1. A thermoplastic branched polycarbonate of high molecularweight possessing flame resistant properties, from(1) a carbonateprecursor: (2) at least one dihydroxyaromatic compound of the formula:##STR6## where: R is a single bond, or R is a substituted ornonsubstituted linear or branched C₁ -C₅ alkylene or R is selected fromthe group consisting of O, S, SO₂ and CO;X and Y, which are the same ordifferent, are H or CH₃ ; m and n, which are the same or different, arewhole numbers from 1 to 4; and (3) at least one halogenatedtriphenolbenzamido compound of the formula: ##STR7## where: Z isselected from the group consisting of CO and SO₂ ;R₁ is chlorine orbromine; and p is 1 or
 2. 2. A polycarbonate as defined in claim 1,having a molar ratio of (3) to (2) of between 0.05/100 and 5/100.
 3. Apolycarbonate as defined in claim 2, having a molar ratio of (3) to (2)of between 0.1/100 and 3/100.
 4. A polycarbonate as defined in claim 1wherein the carbonate precursor (1) is selected from the groupconsisting of phosgene, chloroformyl-terminating polycarbonate oligomershaving a molecular weight of between 400 and 2000, and carbonic aciddiaryl, dialkyl and arylalkyl esters.
 5. A polycarbonate as defined inclaim 1, wherein the dihydroxyaromatic compound is selected from thegroup consisting of:4,4-dihydroxyphenyl;2,2-bis(4-hydroxyphenyl)propane;2,2-bis(3,5-dimethyl-4-hydroxyphenyl)propane; andbis(4-hydroxyphenyl)methane.
 6. A polycarbonate as defined in claim 1,wherein the triphenolbenzamido compound (3) is selected from the groupconsistingof:1,3,5-tris(2'-hydroxy-5'-chlorophenyl)aminocarbonylbenzene;1,3,5-tris(2'-hydroxy-5'-chlorophenyl)aminosulphonylbenzene;1,3,5-tris(4'-hydroxy-2',6'-dichlorophenyl)aminocarbonylbenzene;1,3,5-tris(4'-hydroxy-2',6'-dichlorophenyl)aminosulphonylbenzene; 1.3,5-tris(2'-hydroxy-5'-bromophenyl)aminocarbonylbenzene;and1,3,5-tris(4'-hydroxy-2',6'-dibromophenyl)aminosulphonylbenzene.
 7. Amethod for preparing a polycarbonate as defined in claim 1, comprisingreacting together (1) a carbonate precursor, (2) a dihydroxyaromaticcompound of formula (I), (3) a halogenated triphenolbenzamido compoundof formula (II), the molar ratio of (3) to (2) varying from 0.05/100 to5/100.
 8. A method as defined in claim 7, wherein the carbonateprecursor is selected from the group consisting of phosgene,chloroformyl-terminating polycarbonate oligomers having a molecularweight of between 400 and 2000, and carbonic acid diaryl, dialkyl andarylalkyl esters.
 9. A method as defined in claim 8 wherein thecarbonate precursor is a chloroformyl-terminating polycarbonateoligomer.